Washing machine appliances and methods for operation

ABSTRACT

A washing machine appliance, including methods for operation, is provided herein. The washing machine appliance may have a tub and a basket rotatably mounted to a motor and within the tub. The basket may define a chamber for receipt of articles for washing. The method may include spinning the basket; calculating a torque value; accelerating the basket to an elevated rotational speed; determining an acceleration rate; determining a mass moment of inertia; and adjusting acceleration of the basket.

FIELD OF THE INVENTION

The present subject matter relates generally to washing machine appliances, such as vertical axis washing machine appliances, and methods for monitoring load balance states in such washing machine appliances.

BACKGROUND OF THE INVENTION

Washing machine appliances generally include a cabinet that receives a tub for containing wash and rinse water. A wash basket is rotatably mounted within the wash tub. A drive assembly is coupled to the wash tub and configured to rotate the wash basket within the wash tub in order to cleanse articles within the wash basket. Upon completion of a wash cycle, a pump assembly can be used to rinse and drain soiled water to a draining system.

Washing machine appliances include vertical axis washing machine appliances and horizontal axis washing machine appliances, where “vertical axis” and “horizontal axis” refer to the axis of rotation of the wash basket within the wash tub. Vertical axis washing machine appliances typically have the wash tub suspended in the cabinet with suspension devices. The suspension devices generally allow the tub to move relative to the cabinet during operation of the washing machine appliance.

A significant concern during operation of washing machine appliances is the balance of the tub during operation. For example, articles and water loaded within a basket may not be equally weighted about a central axis of the basket and tub. Accordingly, when the basket rotates, in particular during a spin cycle, the imbalance in clothing weight may cause the basket to be out-of-balance within the tub, such that the axis of rotation does not align with the cylindrical axis of the basket or tub. Such out-of-balance issues can cause the basket to contact the tub during rotation, and can further cause movement of the tub within the cabinet. Significant movement of the tub can cause the tub to contact the cabinet, potentially causing excessive noise, vibration and/or motion or causing damage to the appliance.

Various methods are known for monitoring load balance of washing machine appliances. However, existing methods typically fail to account for increasing or rapid out-of-balance scenarios (i.e., imbalances). As an example, tracking tub strikes or other characteristics of a washing machine appliance may fail to reliably and/or quickly detect imbalances caused by improper water shedding from the basket to the tub. In some instances, water may become trapped or blocked within a portion of wash basket (e.g., by one or more waterproof articles, a foreign object within the basket, a damaged portion of a wash basket, etc.). If the basket enters a ramp or acceleration phase of a cycle, such as during a spin cycle, water may fail to shed or shed unevenly from the basket. The trapped water may be difficult to detect until a high rotational speed is reached, at which point a significant imbalance is already created.

Accordingly, improved methods and apparatus for monitoring load balance in washing machine appliances are desired. In particular, methods and apparatuses that provide accurate monitoring and detection during various ramp or acceleration phases of a cycle would be advantageous.

BRIEF DESCRIPTION OF THE INVENTION

Aspects and advantages of the invention will be set forth in part in the following description, or may be obvious from the description, or may be learned through practice of the invention.

In one aspect of the present disclosure, a method for operating a washing machine appliance is provided. The washing machine appliance may have a tub and a basket rotatably mounted to a motor and within the tub. The basket may define a chamber for receipt of articles for washing. The method may include spinning the basket at a set dwell speed; calculating a torque value based on the set dwell speed; accelerating the basket to an elevated rotational speed; determining an acceleration rate during accelerating the basket; determining a mass moment of inertia based on the calculated torque value and the determined acceleration rate; and adjusting acceleration of the basket according to the determined mass moment of inertia.

In another aspect of the present disclosure, a washing machine appliance is provided. The washing machine appliance may include a tub, a basket, a valve, a nozzle, a motor, and a controller. The basket may be rotatably mounted within the tub. The basket may define a wash chamber for receipt of articles for washing. The nozzle may be configured for flowing liquid from the valve into the tub. The motor may be in mechanical communication with the basket to selectively rotate the basket within the tub. The controller may be in operative communication with the valve and motor. The controller may be configured to initiate an operative cycle. The operative cycle may include spinning the basket at a set dwell speed, calculating a torque value based on the set dwell speed, accelerating the basket to an elevated rotational speed, determining an acceleration rate during accelerating the basket, determining a mass moment of inertia based on the calculated torque value and the determined acceleration rate, and adjusting acceleration of the basket according to the determined mass moment of inertia.

These and other features, aspects and advantages of the present invention will become better understood with reference to the following description and appended claims. The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

A full and enabling disclosure of the present invention, including the best mode thereof, directed to one of ordinary skill in the art, is set forth in the specification, which makes reference to the appended figures.

FIG. 1 provides a perspective view of a washing machine appliance, with a portion of a cabinet of the washing machine appliance shown broken away in order to reveal certain interior components of the washing machine appliance, according to exemplary embodiments of the present disclosure.

FIG. 2 provides a front elevation schematic view of various components of the exemplary washing machine appliance of FIG. 1.

FIG. 3 provides a graph illustrating inertia relative to rotational speed of a basket of an exemplary washing machine appliance for three unique loads wherein water properly sheds from a basket to a tub of the washing machine appliance.

FIG. 4 provides a graph illustrating inertia relative to rotational speed of a basket of an exemplary washing machine appliance for three unique loads.

FIG. 5 provides a flow chart illustrating a method for operating a washing machine appliance in accordance with exemplary embodiments of the present disclosure.

FIG. 6 provides a flow chart illustrating another method for operating a washing machine appliance in accordance with exemplary embodiments of the present disclosure.

FIG. 7 provides a flow chart illustrating yet another method for operating a washing machine appliance in accordance with exemplary embodiments of the present disclosure.

DETAILED DESCRIPTION

Reference now will be made in detail to embodiments of the invention, one or more examples of which are illustrated in the drawings. Each example is provided by way of explanation of the invention, not limitation of the invention. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the scope or spirit of the invention. For instance, features illustrated or described as part of one embodiment can be used with another embodiment to yield a still further embodiment. Thus, it is intended that the present invention covers such modifications and variations as come within the scope of the appended claims and their equivalents.

FIG. 1 provides a perspective view partially broken away of a washing machine appliance 50 according to an exemplary embodiment of the present disclosure. As may be seen in FIG. 1, washing machine appliance 50 includes a cabinet 52 and a cover 54. A backsplash 56 extends from cover 54, and a control panel 58, including a plurality of input selectors 60, is coupled to backsplash 56. Control panel 58 and input selectors 60 collectively form a user interface input for operator selection of machine cycles and features, and in one embodiment a display 61 indicates selected features, a countdown timer, and other items of interest to machine users. A lid 62 is mounted to cover 54 and is rotatable about a hinge (not shown) between an open position (not shown) facilitating access to a wash tub 64 located within cabinet 52, and a closed position (shown in FIG. 1) forming an enclosure over wash tub 64.

As illustrated in FIG. 1, washing machine appliance 50 is a vertical axis washing machine appliance. While the present disclosure is discussed with reference to an exemplary vertical axis washing machine appliance, those of ordinary skill in the art, using the disclosures provided herein, should understand that the subject matter of the present disclosure is equally applicable to other washing machine appliances.

Tub 64 includes a bottom wall 66 and a sidewall 68. Moreover, a basket 70 is rotatably mounted within wash tub 64. In some embodiments, a pump assembly 72 is located beneath tub 64 and basket 70 for gravity assisted flow when draining tub 64. Pump assembly 72 includes a pump 74 and a motor 76. A pump inlet hose 80 extends from a wash tub outlet 82 in tub bottom wall 66 to a pump inlet 84, and a pump outlet hose 86 extends from a pump outlet 88 to an appliance washing machine water outlet 90 and ultimately to a building plumbing system discharge line (not shown) in flow communication with outlet 90.

FIG. 2 provides a front elevation schematic view of certain components of washing machine appliance 50 including wash basket 70 movably disposed and rotatably mounted in wash tub 64 in a spaced apart relationship from tub side wall 68 and tub bottom 66. Basket 70 includes a plurality of perforations therein to facilitate fluid communication between an interior of basket 70 and wash tub 64.

In some embodiments, a hot liquid valve 102 and a cold liquid valve 104 deliver liquid, such as water, to basket 70 and wash tub 64 through a respective hot liquid hose 106 and cold liquid hose 108. Liquid valves 102, 104 and liquid hoses 106, 108 together form a liquid supply connection for washing machine appliance 50 and, when connected to a building plumbing system (not shown), provide a fresh water supply for use in washing machine appliance 50. Liquid valves 102, 104 and liquid hoses 106, 108 are connected to a basket inlet tube 110, and liquid is dispersed from inlet tube 110 through a nozzle assembly 112 having a number of openings therein to direct washing liquid into basket 70 at a given trajectory and velocity. A dispenser (not shown in FIG. 2), may also be provided to produce a liquid or wash solution by mixing fresh water with a known detergent and/or other additive for cleansing of articles in basket 70.

As illustrated, an agitation element 116, such as a vane agitator, impeller, auger, or oscillatory basket mechanism, or some combination thereof, may be disposed in basket 70 to impart an oscillatory motion to articles and liquid in basket 70. In various exemplary embodiments, agitation element 116 may be a single action element (oscillatory only), double action (oscillatory movement at one end, single direction rotation at the other end) or triple action (oscillatory movement plus single direction rotation at one end, single direction rotation at the other end). As illustrated, agitation element 116 is oriented to rotate about a vertical axis 118.

Basket 70 and agitation element 116 are driven by a motor 120 through a transmission and clutch system 122. The motor 120 drives shaft 126 to rotate basket 70 within wash tub 64. Clutch system 122 facilitates driving engagement of basket 70 and agitation element 116 for rotatable movement within wash tub 64, and clutch system 122 facilitates relative rotation of basket 70 and agitation element 116 for selected portions of wash cycles. Motor 120 and transmission and clutch system 122 collectively are referred herein as a motor assembly 148.

Basket 70, tub 64, and motor assembly 148 are supported by a vibration dampening suspension system. The dampening suspension system can include one or more suspension assemblies 92 coupled between and to the cabinet 52 and wash tub 64. Typically, four suspension assemblies 92 are utilized, and are spaced apart about the wash tub 64. For example, each suspension assembly 92 may be connected at one end proximate a corner of the cabinet 52 and at an opposite end to the wash tub 64. The washer can include other vibration dampening elements, such as a balance ring 94 disposed around the upper circumferential surface of the wash basket 70. The balance ring 94 can be used to counterbalance an out of balance condition for the wash machine as the basket 70 rotates within the wash tub 64. The wash basket 70 could also include a balance ring 96 located at a lower circumferential surface of the wash basket 70.

A dampening suspension system generally operates to dampen dynamic motion as the wash basket 70 rotates within the tub 64. The dampening suspension system has various natural operating frequencies of the dynamic system. These natural operating frequencies are referred to as the modes of suspension for the washing machine. For instance, the first mode of suspension for the washing machine occurs when the dynamic system including the wash basket 70, tub 64, and suspension system are operating at the first resonant or natural frequency of the dynamic system.

Operation of washing machine appliance 50 is controlled by a controller 150 that is operatively coupled (e.g., electrically coupled or connected) to the user interface input located on washing machine backsplash 56 (FIG. 1) for user manipulation to select washing machine cycles and features. In response to user manipulation of the user interface input, controller 150 operates the various components of washing machine appliance 50 to execute selected machine cycles and features.

Controller 150 may include a memory (e.g., non-transitory storage media) and microprocessor, such as a general or special purpose microprocessor operable to execute programming instructions or micro-control code associated with a washing operation or cycle. The memory may represent random access memory such as DRAM, or read only memory such as ROM or FLASH. In one embodiment, the processor executes programming instructions stored in memory (e.g., as software). The memory may be a separate component from the processor or may be included onboard within the processor. Alternatively, controller 150 may be constructed without using a microprocessor, e.g., using a combination of discrete analog and/or digital logic circuitry (such as switches, amplifiers, integrators, comparators, flip-flops, AND gates, and the like) to perform control functionality instead of relying upon software. Control panel 58 and other components of washing machine appliance 50 (such as motor assembly 148 and measurement devices 130—discussed herein) may be in communication with controller 150 via one or more signal lines or shared communication busses to provide signals to and/or receive signals from the controller 150. Optionally, a measurement device 130 may be included with controller 150. Moreover, measurement devices 130 may include a microprocessor that performs the calculations specific to the measurement of motion with the calculation results being used by controller 150.

In specific embodiments, one or more measurement devices 130 are provided in the washing machine appliance 50 for measuring movement of the tub 64 during one or more portions of an operative cycle (e.g., a wash cycle, rinse cycle, spin cycle, etc.). Generally, movement may be measured as one or more angular positions, speeds, and/or accelerations, detected at the one or more measurement devices 130. Measurement devices 130 may measure a variety of suitable variables, which can be correlated to movement of the tub 64. The movement measured by such devices 130 can be utilized to monitor the load balance state of the tub 64 (e.g., during a spin cycle), and to facilitate movement or acceleration in particular manners and/or for particular time periods to prevent damage or undesired operations.

A measurement device 130 in accordance with the present disclosure may include an accelerometer which measures translational motion, such as acceleration along one or more directions. Additionally or alternatively, a measurement device 130 may include a gyroscope, encoder, or other measurement devices, which measures rotational motion, such as rotational velocity about an axis. In some embodiments, measurement device 130 is mounted to the tub 64 (e.g., bottom wall 66 or a sidewall 68 thereof) to sense movement of the tub 64 relative to the cabinet 52 by measuring uniform periodic motion, non-uniform periodic motion, and/or excursions of the tub 64 during appliance 50 operation. In additional or alternative embodiments, measurement device 130 is mounted to a separate portion of appliance 50 (e.g., on or within backsplash 56) to sense movement of the cabinet 52 by measuring uniform periodic motion, non-uniform periodic motion, and/or excursions during appliance 50 operation.

In exemplary embodiments, a measurement device 130 may include at least one gyroscope and/or at least one accelerometer. The measurement device 130, for example, may be a printed circuit board which includes the gyroscope and accelerometer thereon. The measurement device 130 may be mounted to the tub 64 (e.g., via a suitable mechanical fastener, adhesive, etc.) and may be oriented such that the various sub-components (e.g., the gyroscope and accelerometer) are oriented to measure movement along or about particular directions. Notably, the gyroscope and accelerometer in exemplary embodiments may be mounted to the tub 64 at a single location (e.g., the location of the printed circuit board or other component of the measurement device 130 on which the gyroscope and accelerometer are grouped). Such positioning at a single location advantageously reduces the costs and complexity (e.g., due to additional wiring, etc.) of out-of-balance detection, while still providing relatively accurate out-of-balance detection as discussed herein. Alternatively, however, the gyroscope and accelerometer need not be mounted at a single location. For example, a gyroscope located at one location on tub 64 can measure the rotation of an accelerometer located at a different location on tub 64, because rotation about a given axis is the same everywhere on a solid object such as tub 64.

In an illustrative embodiment, laundry items are loaded into basket 70, and washing operation is initiated through operator manipulation of control input selectors 60 (FIG. 1). Tub 64 is filled with liquid such as water and mixed with detergent to form a wash fluid, and basket 70 is agitated with agitation element 116 for cleansing of laundry items in basket 70. That is, agitation element 116 is moved back and forth in an oscillatory back and forth motion about vertical axis 118, while basket 70 remains generally stationary (i.e., not actively rotated).

In exemplary embodiments, agitation element 116 is rotated clockwise a specified amount about the vertical axis 118 of the machine, and then rotated counterclockwise by a specified amount. The clockwise/counterclockwise reciprocating motion is sometimes referred to as a stroke, and the agitation phase of the wash cycle constitutes a number of strokes in sequence. Acceleration and deceleration of agitation element 116 during the strokes imparts mechanical energy to articles in basket 70 for cleansing action. The strokes may be obtained in different embodiments with a reversing motor, a reversible clutch, or other known reciprocating mechanism. After the agitation phase of the wash cycle is completed, tub 64 is drained with pump assembly 72. Laundry articles can then be rinsed by again adding liquid to tub 64. Depending on the particulars of the cleaning cycle selected by a user, agitation element 116 may again provide agitation within basket 70.

After a rinse cycle, tub 64 is again drained, such as through use of pump assembly 72. After liquid is drained from tub 64, one or more spin cycles may be performed. In particular, a spin cycle may be applied after the agitation phase and/or after the rinse phase in order to wring excess wash fluid from the articles being washed. During a spin cycle, basket 70 is rotated at relatively high speeds about vertical axis 118, such as between approximately 450 and approximately 1300 revolutions per minute. For instance, upon reaching a single dwell speed, basket 70 may be accelerated to a terminal high speed velocity across one or more ramp phases.

Turning briefly to FIGS. 3 and 4, graphs illustrating the measured mass-moment of inertia (MMI) (e.g., in kilogram-meters squared—kg*m²) of a washing machine appliance 50 in relation to the measured rotational speed (e.g., in revolutions per minute—RPM) of the basket 70 of the washing machine appliance 50 about the vertical axis. For example, a controller 150 of the washing machine appliance 50 may measure MMI based on acceleration data or signals received from a measurement device 130 mounted on or within the washing machine appliance 50. The measured MMI may additionally or alternatively be based on electrical current data or signals received from a motor 120 attached to the basket 70 (e.g., electrical current output signals). Moreover, the controller 150 may measure rotational speed based on velocity data or signals received by the measurement device 130 and/or motor 120.

Generally, FIG. 3 illustrates measured changes in MMI across a range of rotational speeds for three unique loads, 3-1, 3-2, and 3-3 during an exemplary operative cycle of a washing machine appliance 50. Specifically, the graph of FIG. 3 illustrates three unique balanced loads during a spin cycle. For instance, the spin cycle of FIG. 3 may immediately follow an agitation cycle or rinse cycle (e.g., after water is initially drained from a tub 64 via pump assembly 72). As illustrated, during a first ramp phase 310, the wash basket 70 of the washing machine appliance 50 accelerates from an initial dwell speed (e.g., 140 RPM) to an intermediate speed (e.g., 450 RPM). Articles within the basket 70 may be forced against an interior wall of the basket 70. The first ramp phase 310 may thus be considered a plastering phase. A second ramp phase 320 may follow the first ramp phase 310 as the basket 70 further accelerates from the intermediate speed to a terminal or final speed (e.g., 700 RPM). As illustrated, in the second ramp phase 320, torque applied to the basket 70 may settle during an adjustment sub-phase 322. Once torque has settled, MMI generally decreases over a final sub-phase 324. During this second ramp phase 320, water is evenly shed from the basket 70, decreasing the mass within the basket.

Similarly to FIG. 3, FIG. 4 illustrates measured changes in MMI across a range of rotational speeds for three unique loads, 4-1, 4-2, and 4-3 during an exemplary spin cycle of a washing machine appliance 50. However, in contrast to FIG. 3, FIG. 4 illustrates two out-of-balance loads (4-2 and 4-3), along with one balanced load (4-1). Specifically, the loads 4-2 and 4-3 illustrate exemplary testing conditions wherein a controlled increasing out-of-balance load was placed within the basket 70. The spin cycle of FIG. 4 may immediately follow an agitation cycle or rinse cycle (e.g., after water is initially drained from a tub 64). As illustrated, during a first ramp phase 410, the wash basket 70 of the washing machine appliance 50 accelerates from an initial set dwell speed (e.g., 140 RPM) to an intermediate speed (e.g., 450 RPM). As with the exemplary loads of FIG. 3, articles within the basket 70 may be forced against an interior wall of the basket 70. A second ramp phase 420 may also follow the first ramp phase 410 as the basket 70 further accelerates from the intermediate speed to a terminal or final speed (e.g., 700 RPM). During the first ramp phase 410, it may be difficult to observe or detect any potential out-of-balance condition. However, an out-of-balance condition may be created as the washing machine appliance 50 attempts to shed water during the second ramp phase 420. In the case of a balanced load (e.g., 4-1) MMI generally decreases over the second ramp phase 420. By contrast, in the case of an out-of-balance load (e.g., 4-2 and 4-3), MMI increases over the second ramp phase 420 as water fails to shed evenly from the basket 70.

Returning to FIGS. 1 and 2, in some embodiments, controller 150 is generally configured to initiate an operative cycle of washing machine appliance 50. In some such embodiments, controller 150 is further configured to detect and address out-of-balance conditions, such as those illustrated in FIG. 4 at loads 4-2 and 4-3. In certain embodiments, controller 150 actively or continuously monitors conditions at the motor 120 as it rotates basket 70. Specifically, controller 150 may monitor the mass moment of inertia (MMI) during the operative cycle. During certain cycles or phases, an elevated MMI (e.g., an MMI value, MMI slope value, jerk value, acceleration value, etc. above a threshold value) or MMI pattern (e.g., of maximum and/or minimum MMI values) may indicate an out-of-balance condition. Accordingly, rotation or acceleration of the basket 70 may be adjusted to limit further increases in the MMI of the washing machine appliance 50.

In exemplary embodiments, controller 150 is configured to determine (e.g., continuously or repeatedly) an MMI value for the motor 120 during a spin cycle. A volume of liquid be flowed into the tub 64 (e.g., as part of a wash cycle or rinse cycle) and/or drained before the spin cycle begins. The spin cycle may thus serve to wring remaining liquid from articles within basket 70. As an example, the spin cycle may include an initial dwell speed at which the controller 150 directs motor 120 to rotate basket 70. After the initial dwell speed (e.g., after a predetermined amount of time of rotating basket 70 at the initial dwell speed), the spin cycle may accelerate along one or more ramp phases. Generally, acceleration may continue until a predetermined terminal velocity is reached or controller 150 directs controller 150 to adjust or restrict acceleration. Advantageously, potential imbalances may be detected and addressed before the terminal velocity is reached.

In some such embodiments, the MMI value may be based on a calculated torque and an associated contemporary acceleration rate of motor 120 at a specific point in time. For example, a torque equation may be stored as a predetermined or set regression equation within controller 150 (e.g., at the memory). The regression equation may be based on testing data gathered from an exemplary unit of a certain model of washing machine appliance 50. Moreover, the regression equation for torque may be constructed such that variable values of rotational speed and/or electrical current, voltage, or power (e.g., detected at motor 120) may be input for torque determinations. As an example, the torque regression equation may be set as

(Equation 1)

T=(A*ω ² *I ²)+(B*I ²)+(C*ω ²)+(D*ω*I)+(E*I)+(F*ω)+G

-   -   wherein T represents the calculated torque value,     -   wherein A, B, C, D, E, F, and G represent predetermined         coefficients of the washing machine appliance 50 (e.g., stored         within controller 150),     -   wherein ω represents an associated rotational speed, and     -   wherein I represents a measured electrical current at the motor         120.

Controller 150 may generally measure the current delivered to motor 120 as electrical current (1), while a signal is received (e.g., simultaneously) from motor 120 to indicate or determine an associated rotational speed (ω) of the basket 70 (e.g., a rotational speed associated in time with a specific and respective electrical current, I). In turn, a specific torque value (T₁) is based on a specific associated electrical current (I₁) and rotational speed (ω₁). Acceleration (α) may be determined, for instance, by calculating changes in rotational speed over time (i.e., a α=Δω/Δt), based on signals received (e.g., from motor 120). In turn, a specific acceleration (α₁) may be a value of radians per second based on the change in speed (ω₁-ω₀) during an associated time period (t₁-t₀).

In additional or alternative embodiments, controller 150 may be configured to determine an MMI value based on a friction coefficient (FC) for washing machine appliance 50, e.g., at motor 120. Since friction may change over time or for a given load, a new friction coefficient (FC) may be calculated for each new load (e.g., each new spin cycle). As an example, a specific friction coefficient may calculated as

(Equation 2)

FC=T ₀−(VC* ω ₀)

-   -   wherein FC represents the friction coefficient for a specific         load,     -   wherein T₀ represents the associated calculated torque value at         the dwell speed,     -   wherein VC represents a predetermined dampening coefficient of         the washing machine appliance (e.g., stored within controller         150), and     -   wherein ω₀ represents the dwell speed.

During the ramp phase(s) following a dwell phase, controller 150 may be configured to calculate MMI repeatedly. For example, MMI may be calculated as

(Equation 3)

MMI=(T−VC*ω−FC)/α

-   -   wherein MMI represents a specific mass moment of inertia,     -   wherein T represents an associated calculated torque value,     -   wherein VC represents the predetermined dampening coefficient,     -   wherein ω represents an associated rotational speed, and     -   wherein α represents an associated acceleration magnitude.

In some embodiments, controller 150 is configured to actively compare calculated MMI value(s) to one or more threshold inertia (e.g., predetermined threshold value). Optionally, a threshold inertia may correspond to specific phase, period, or condition (e.g., second ramp phase 320, elapsed time of the spin cycle, rotational speed of the motor 120, range of rotational speeds of the motor 120, etc.).

In additional or alternative embodiments, controller 150 is configured to further calculate a modified value. As an example, the modified value may include a calculated MMI ratio (e.g., calculated MMI value over a predetermined MMI value). As another example, the modified value may include one or more value derived from data set (e.g., graph) of inertia (e.g., MMI) as a function of time, such as an acceleration value or jerk value. A slope of the data set or graph, as well as a ripple in the data set or graph, may further be detected.

If the calculated MMI value or modified value equals or exceeds the threshold inertia, controller 150 may adjust acceleration. For instance, controller 150 may initiate a redistribution phase wherein agitator 116 and/or basket 70 may be rotated (e.g., in alternate clockwise and counter-clockwise movements). Additionally or alternatively, acceleration may be halted or reduced. For instance, a new terminal speed may be set and/or rotational speed of the basket 70 may be reduced to complete the spin cycle.

Referring now to FIGS. 5 through 7, various methods may be provided for use with washing machine appliances (e.g., washing machine appliance 50) in accordance with the present disclosure. In general, the various steps of methods as disclosed herein may, in exemplary embodiments, be performed by the controller 150 as part of an operative cycle that the controller 150 is configured to initiate (e.g., a wash cycle, a rinse cycle, a spin cycle, etc.). During such methods, controller 150 may receive inputs and transmit outputs from various other components of the appliance 50. For example, controller 150 may send signals to and receive signals from motor assembly 148 (including the motor 120), control panel 58, one or more measurement device 130, pump assembly 72, and/or valves 102, 104. In particular, the present disclosure is further directed to methods, as indicated by reference numbers 500, 600, and 700, for operating washing machine appliance. Such methods advantageously facilitate monitoring of load balance states, detection of out-of-balance conditions, and reduction of out-of-balance conditions when detected. In exemplary embodiments, such balancing is performed during a spin cycle or phase.

FIGS. 5 through 7 depict steps performed in a particular order for purpose of illustration and discussion. Those of ordinary skill in the art, using the disclosures provided herein, will understand that (except as otherwise indicated) the steps of any of the methods disclosed herein can be modified, adapted, rearranged, omitted, or expanded in various ways without deviating from the scope of the present disclosure.

Turning specifically to FIG. 5, a method 500 is illustrated. At 510, the method 500 may include flowing a volume of a liquid into the tub. The liquid may include water, and may further include one or more additives as discussed above. The water may be flowed through the hot liquid hose and/or cold liquid hose, the basket inlet tube, and nozzle assembly into the tub and onto articles that are disposed in the basket for washing. The volume of liquid may be dependent upon the size of the load of articles and other variables which may, for example, be input by a user interacting with the control panel and input selectors thereof.

At 520, the method 500 may include spinning the basket at a set dwell speed. For instance, the motor may rotate the basket within tub at the set dwell speed (e.g., in rotations per minute) for a predetermined time period (i.e., a predetermined amount of time). In some such embodiments, 520 follows 510 and/or another cycle, such as a wash cycle, rinse cycle, drain cycle, etc. Optionally, the pump assembly may draw water (e.g., at least a portion of the volume of liquid from 510) away from the tub before spinning begins.

At 530, the method 500 may include calculating a torque value of the motor at a certain point or phase. The torque value may be based on a rotational speed of the motor during the certain point or phase. Additionally or alternatively, the torque value may be based on the electrical current measured at the motor during the certain point of phase. A predetermined equation may be provided for calculating the torque value. For example, a set torque regression equation may be stored within the controller, such as Equation 1 described above. In some embodiments, 530 occurs at least once during the method 500. For instance, a torque value at the dwell speed of 520 may be calculated. In additional or alternative embodiments, 530 may be repeated throughout the method 500. In turn, torque values may be repeatedly calculated (e.g., during one or more acceleration or ramp phases) for the motor while rotating the basket.

In optional embodiments, the method 500 may further include determining a friction coefficient for a given load within the wash basket (i.e., the given load being treated during through the method 500). Specifically, the determination of the friction coefficient may be based on the set dwell speed. Moreover, the friction coefficient may be based on a calculated torque value at the set dwell speed. Thus, the friction coefficient may be a specific value that is contingent upon the actual or real-time conditions while the given load is being treated, advantageously increasing accuracy of corresponding calculations, determinations, or measurements.

In additional or alternative embodiments, the friction coefficient of method 500 may be based on a predetermined damping coefficient for the washing machine appliance (e.g., the damping coefficient for movement of the basket within the tub). As an example, the friction coefficient of a given load in method 500 may be determined as the difference between the calculated torque value at the set dwell speed and the product of the predetermined damping coefficient times the set dwell speed, as described above with respect to Equation 2. Advantageously, the determination of the friction coefficient may require relatively little processing power from the controller. Moreover, the determination of the friction coefficient may be performed, for example, during 520, advantageously preventing the overall cycle time (i.e., time required to perform method 500) from being increased.

At 540, the method 500 includes accelerating the basket to an elevated rotational speed. Specifically, 540 may immediately follow 530. In turn, 540 may increase the rotational speed from the set dwell speed to the elevated rotational speed. In other words, the elevated rotational speed is a velocity greater than the set dwell speed. In some embodiments, the elevated rotational speed may be a predetermined final or terminal speed for the basket. As an example, 540 may include increasing the rotational speed of the basket from the set dwell speed to a higher intermediate speed (e.g., during a first ramp phase) before further increasing the rotational speed of the basket from the intermediate speed to the predetermined terminal speed (e.g., during a second ramp phase). Optionally, no secondary dwell speed may be required between the set dwell speed and the predetermined terminal speed. In other words, 540 may provide for continuous acceleration from the set dwell speed to the predetermined terminal speed.

At 550, the method 500 includes determining a contemporary acceleration rate of the motor. For instance, the controller may determine the acceleration from multiple signals received from the motor. In some such embodiments, the contemporary acceleration rate may be calculated (e.g., in radians per second) as the difference between two received rotational speed signals over the change in time between the two received rotational speed signals. In some embodiments, contemporary acceleration rate of 550 is determined during a portion of 540 (e.g., during one or more ramp phase).

At 560, the method 500 includes determining a mass moment of inertia based on the calculated torque at 530 and the determined contemporary acceleration rate at 550. The mass moment of inertia may generally correspond to a specific period or point, such as the period or point associated with the determined acceleration rate at 550. In certain embodiments, the mass moment of inertia of 560 is further based on a contemporary torque value from the motor (e.g., a determined torque value associated with or corresponding to the contemporary acceleration of 550). The contemporary torque may be modified by one or more values based on the determined friction coefficient for the load and/or the predetermined damping coefficient for the washing machine appliance.

As an example, the mass moment of inertia of 560 may be determined as a single value of the division between an adjusted torque value over the contemporary acceleration, as described above with respect to Equation 3. In turn, the adjusted torque value may be determined as the value of the contemporary torque value minus the predetermined friction coefficient and a product of the determined friction coefficient times a rotational speed associated with the torque value. In some embodiments, mass moment of inertia of 560 is determined during a portion of 540 (e.g., during one or more ramp phase). In further embodiments, 550 may be repeated throughout the method 500. In turn, torque values may be repeatedly calculated (e.g., during one or more acceleration or ramp phases) for the motor while rotating the basket.

Although a single mass moment of inertia value may be utilized at 560, it is understood that additional or alternative embodiments may include a modified value (e.g., a calculated MMI ratio, an acceleration value, a jerk value, a slope value, ripple, etc.) as described above.

At 570, the method 500 includes adjusting acceleration of the basket according to the determined mass moment of inertia. In some embodiments, 570 includes comparing the determined mass moment of inertia at 560 to a threshold inertia (e.g., stored within the controller). If the determined mass moment of inertia is less than or equal to the threshold inertia, acceleration may continue. For instance, 550 may continue until the predetermined terminal speed is reached. If the determined mass moment of inertia exceeds the threshold inertia, acceleration of the basket may be restricted. As an example, 570 may include directing the motor to halt acceleration in response to the threshold inertia being exceeded. The motor may be rotated at a reduced rotational speed. Additionally or alternatively, a new terminal speed may be set (e.g., from a correlated chart, graph, or reference table stored within the controller). As another example, 570 may include initiating a redistribution phase in response to the threshold inertia being exceeded. The agitator and/or basket may be rotated (e.g., in alternate clockwise and counter-clockwise movements) to move articles within the basket and release any trapped liquids.

Turning specifically to FIG. 6, a method 600 is illustrated. At 610, the method 600 may include initiating a spin cycle. For example, the spin cycle may be initiated as part of a larger wash operation (e.g., a wash operation selected by a user input). In turn, the spin cycle may follow one or more cycle or phase, such as a wash cycle or rinse cycle, in which water is flowed to the tub of the washing machine appliance. In some such embodiments, the spin cycle may follow a drain cycle in which a drain in communication with the tub is opened to flow a volume of water away from the tub and basket.

At 620, the method 600 may include rotating the basket at a dwell speed. The dwell speed may be set or programed within a controller for the spin cycle. The motor may rotate the basket within tub at the set dwell speed (e.g., in rotations per minute) for a predetermined time period (i.e., a predetermined amount of time).

At 630, the method 600 may include calculating a friction coefficient. Specifically, the friction coefficient may be calculated for the load being treated during the spin cycle. In some such embodiments, the friction coefficient may be calculated based on the dwell speed as well as an associated torque value of the motor at the dwell speed. The friction coefficient may be further based on a predetermined damping coefficient for the washing machine appliance (e.g., the damping coefficient for movement of the basket within the tub). As an example, the friction coefficient of 630 may be determined as the difference between the calculated torque value at the set dwell speed and the product of the predetermined damping coefficient times the set dwell speed, as described above with respect to Equation 2. Optionally, 630 may occur during or after 620.

At 640, the method 600 may include evaluating the pump pressure at the pump assembly of the washing machine appliance. If a set pump pressure is satisfied (e.g., if the evaluated pump pressure is greater than or equal to a threshold pressure), 640 may be immediately followed by a first ramp phase at 642 wherein the basket is accelerated to a second speed (e.g., a second rotational speed that is greater than the dwell speed). If the set pump pressure is not satisfied (e.g., if the evaluated pump pressure is less than the threshold pressure), 640 may lead immediately to a reset phase at 644 wherein the basket is filled (e.g., refilled) with a volume of water, the basket is rotated within tub, and the basket is drained of the volume of water before returning to 620.

While the basket is accelerating to the second speed at 642, the method 600 may include tracking mass moment of inertia for the basket at 650. At 650, mass moment of inertia may be repeatedly calculated. In other words, multiple values for mass moment of inertia may be calculated. Each value of mass moment of inertia may correspond to an associated contemporary acceleration value (e.g., repeatedly calculated, as described above). Moreover, each value of mass moment of inertia may be based on the associated acceleration value, as well as a contemporary torque from the motor (e.g., a determined torque value associated with or corresponding to the contemporary acceleration). The contemporary torque may be modified by one or more values based on the determined friction coefficient for the load and/or the predetermined damping coefficient for the washing machine appliance. Each value of mass moment of inertia may be determined as division between an adjusted torque value over the contemporary acceleration value, as described above with respect to Equation 3. In turn, the adjusted torque value may be determined as the value of the contemporary torque value minus the predetermined friction coefficient and a product of the determined friction coefficient times a rotational speed associated with the torque.

At 660, the method 600 may include evaluating the mass moment of inertia at 650. In turn, 660 may be repeated in tandem with each new mass moment of inertia calculated at 650. In some embodiments, 660 includes comparing the mass moment of inertia at 650 to an expected inertia value. If the mass moment of inertia at 650 is greater than the expected inertia value, 660 may be immediately followed by 644. If the mass moment of inertia is less than or equal to the expected inertia value, 660 may be immediately followed by a second ramp phase at 642 wherein the basket is accelerated to a third speed (e.g., a third rotational speed that is greater than the second speed).

While the basket is accelerating to the third speed at 662, the method 600 may include tracking mass moment of inertia for the basket at 670. At 670, mass moment of inertia may be repeatedly calculated. In other words, multiple values for mass moment of inertia may be calculated. Each value of mass moment of inertia may correspond to an associated contemporary acceleration value. Moreover, each value of mass moment of inertia may be based on the associated acceleration value, as well as a contemporary torque from the motor (e.g., a determined torque value associated with or corresponding to the contemporary acceleration).

At 680, the method 600 may include evaluating the mass moment of inertia at 670. In turn, 680 may be repeated in tandem with each new mass moment of inertia calculated at 670. In some embodiments, 660 includes comparing the mass moment of inertia at 650 to an expected inertia value (e.g., a new inertia value that is less than the expected inertia value of 660). If the mass moment of inertia at 680 is greater than the expected inertia value, 670 may be immediately followed by 644. If the mass moment of inertia is less than or equal to the expected inertia value, the method 600 may permit the spin cycle to continue (e.g., until the predetermined final speed is reached).

Turning specifically to FIG. 7, a method 700 is illustrated. At 710, the method 700 may include initiating a spin cycle. For example, the spin cycle may be initiated as part of a larger wash operation (e.g., a wash operation selected by a user input). In turn, the spin cycle may follow one or more cycle or phase, such as a wash cycle or rinse cycle, in which water is flowed to the tub of the washing machine appliance. In some such embodiments, the spin cycle may follow a drain cycle in which a drain in communication with the tub is opened to flow a volume of water away from the tub and basket.

At 720, the method 700 may include assessing a friction coefficient. Specifically, 720 includes evaluating whether a friction coefficient is known or determined for the spin cycle initiated at 710. If the friction coefficient is not known, 720 may include determining the friction coefficient. Specifically, the basket may be rotated at a dwell speed. At the dwell speed, an associated torque may be determined, as described above. Upon the associated torque being determined, the friction coefficient may be calculated. Along with the associated torque, the friction coefficient may be further based on a predetermined damping coefficient for the washing machine appliance (e.g., the damping coefficient for movement of the basket within the tub). In turn, the friction coefficient of 720 may be determined as the difference between the calculated torque value at the set dwell speed and the product of the predetermined damping coefficient times the set dwell speed, as described above with respect to Equation 2. Once the friction coefficient is determined at 720, the method 700 may proceed to 730. If the friction is known at the beginning of 720, the method may immediately proceed to 730 (i.e., without calculating a new friction coefficient).

At 730, the method 700 may include evaluating rotation of the basket. Specifically, 730 may include receiving multiple rotational speed signals (e.g., from the motor) at discrete points in time. From the received rotational speed signals, it may be determined whether rotation of the basket is accelerating. If the basket is not accelerating (i.e., if the rotational speed of the basket is not increasing), the method 700 may proceed immediately to 750, described below. If the basket is accelerating (i.e., if the rotational speed of the basket is increasing), the basket may proceed to 742.

At 742, the method 700 may include assessing a mass moment of inertia for the basket. Specifically, mass moment of inertia may be repeatedly calculated. In other words, multiple values for mass moment of inertia may be calculated. Each value of mass moment of inertia may correspond to an associated contemporary acceleration value (e.g., repeatedly calculated, as described above). Moreover, each value of mass moment of inertia may be based on the associated acceleration value, as well as a contemporary torque value from the motor (e.g., a determined torque value associated with or corresponding to the contemporary acceleration). The contemporary torque value may be modified by one or more values based on the determined friction coefficient for the load and/or the predetermined damping coefficient for the washing machine appliance. Each value of mass moment of inertia may be determined as division between an adjusted torque value over the contemporary acceleration value, as described above with respect to Equation 3. In turn, the adjusted torque value may be determined as the resultant value of the contemporary torque value minus the predetermined friction coefficient and a product of the determined friction coefficient times a rotational speed associated with the contemporary torque value.

At 744, the method 700 may include evaluating the mass moment of inertia at 742. In turn, 744 may be repeated in tandem with each new mass moment of inertia calculated at 742. In some embodiments, 744 includes comparing the mass moment of inertia at 742 to an expected inertia value. If the mass moment of inertia at 744 is greater than the expected inertia value, 744 may be immediately followed by 746. If the mass moment of inertia is less than or equal to the expected inertia value, 744 may be immediately followed by 750.

At 746, the method 700 may include redistributing the load within the basket. For instance, the agitator and/or basket may be rotated (e.g., in alternate clockwise and counter-clockwise movements) to move articles within the basket and release any trapped liquids. Additionally or alternatively, acceleration may be halted or reduced. Upon 746 being completed, the method 700 may return to 730.

At 750, the method 700 may include establishing the rotational speed. In other words, the current or contemporary rotational speed may be determined. For instance, a rotational signal may be received (e.g., from the motor). From the received rotational speed signal, the rotational speed may be determined.

At 760, the method 700 may include evaluating the established rotational speed. Specifically, 760 may include determining if the established rotational speed is greater than or equal to a set final speed. If the established speed is less than the set final speed, the method 700 may return to 730. If the established speed is greater than or equal to the set final speed, the method 700 may permit the spin cycle to continue.

This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they include structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims. 

What is claimed is:
 1. A method for operating a washing machine appliance, the washing machine appliance having a tub and a basket rotatably mounted to a motor and within the tub, the basket defining a chamber for receipt of articles for washing, the method comprising: spinning the basket at a set dwell speed; calculating a torque value based on the set dwell speed; accelerating the basket to an elevated rotational speed; determining an acceleration rate during accelerating the basket; determining a mass moment of inertia based on the calculated torque value and the determined acceleration rate; and adjusting acceleration of the basket according to the determined mass moment of inertia.
 2. The method of claim 1, further comprising determining a friction coefficient based on the set dwell speed, wherein the determined mass moment of inertia is further based on the friction coefficient.
 3. The method of claim 2, wherein the determined friction coefficient is further based on a predetermined damping coefficient.
 4. The method of claim 2, wherein the determined mass moment of inertia is further based on a predetermined damping coefficient.
 5. The method of claim 2, wherein the determined friction coefficient is further based on the calculated torque value.
 6. The method of claim 1, wherein determining a mass moment of inertia occurs during accelerating the basket.
 7. The method of claim 6, further comprising repeating determining a mass moment of inertia during accelerating the basket.
 8. The method of claim 1, wherein calculating the torque value comprises utilizing a set torque regression equation comprising a rotational speed value, electrical current value, an electrical voltage value, or an electrical power value.
 9. The method of claim 1, wherein calculating the torque value comprises utilizing a set torque regression equation comprising T=(A*ω ² *I ²)+(B*I ²)+(C*ω ²)+(D*ω*I)+(E*I)+(F*ω)+G wherein T represents the torque value, wherein A, B, C, D, E, F, and G represent predetermined coefficients of the washing machine appliance, wherein ω represents an associated rotational speed of the basket, and wherein I represents a measured electrical current at the motor.
 10. A washing machine appliance, comprising: a tub; a basket rotatably mounted within the tub, the basket defining a wash chamber for receipt of articles for washing; a valve; a nozzle configured for flowing liquid from the valve into the tub; a motor in mechanical communication with the basket to selectively rotate the basket within the tub; and a controller in operative communication with the valve and motor, the controller configured to initiate an operative cycle comprising spinning the basket at a set dwell speed, calculating a torque value based on the set dwell speed, accelerating the basket to an elevated rotational speed, determining an acceleration rate during accelerating the basket, determining a mass moment of inertia based on the calculated torque value and the determined acceleration rate, and adjusting acceleration of the basket according to the determined mass moment of inertia.
 11. The washing machine appliance of claim 10, wherein the operative cycle further comprises determining a friction coefficient based on the set dwell speed, wherein the determined mass moment of inertia is further based on the friction coefficient.
 12. The washing machine appliance of claim 11, wherein the determined friction coefficient is further based on a predetermined damping coefficient.
 13. The washing machine appliance of claim 11, wherein the determined mass moment of inertia is further based on a predetermined damping coefficient.
 14. The washing machine appliance of claim 11, wherein the determined friction coefficient is further based on the calculated torque value.
 15. The washing machine appliance of claim 10, wherein determining a mass moment of inertia occurs during accelerating the basket.
 16. The washing machine appliance of claim 15, wherein the operative cycle further comprises repeating determining a mass moment of inertia during accelerating the basket.
 17. The washing machine appliance of claim 10, wherein calculating the torque value comprises utilizing a set torque regression equation comprising a rotational speed value, electrical current value, an electrical voltage value, or an electrical power value.
 18. The washing machine appliance of claim 10, wherein calculating the torque value comprises utilizing a set torque regression equation comprising T=(A*ω ² *I ²)+(B*I ²)+(C*ω ²)+(D*ω*I)+(E*I)+(F*ω)+G wherein T represents the torque value, wherein A, B, C, D, E, F, and G represent predetermined coefficients of the washing machine appliance, wherein ω represents an associated rotational speed, and wherein I represents a measured electrical current at the motor. 